The goal of this research is to elucidate the cellular and molecular processes that underlie sensory organ formation during inner ear development. The proposed research will use the auditory and vestibular system of Xenopus laevis and Xenopus (Silurana) tropicalis as experimental models. Results are expected to provide comparative data about the structure, growth, and genetic profile of three inner ear endorgans: the sacculus (an acoustico-vestibular organ) and the amphibian papilla (an acoustic organ). Experiments will focus on cells of the peripheral nervous system: mechanosensory hair cells and sensory ganglion cells. A major long term goal of this research is to develop technologies and methods for identifying novel genes expressed in the inner ear. The specific aims are: (1) to obtain methods for identifying novel genes expressed in the inner ear. The specific aims are: (1) to obtain comparative data about pattern formation during development of the sensory epithelial of the utricle, amphibian papilla, and sacculus, (2) to identify the sites of hair cell and sensory ganglion cell production during ear development, (3) to synthesize cDNA libraries from the inner ear of X. laevis and X. tropicalis, and (4) to analyze gene expression patterns of inner ear cDNA library clones. Methods used in this research include RT-PCR directed cDNA library construction, isolation of RNA from small quantities of inner ear tissue, in situ hybridization, bioinformatics, and multi-photon laser scanning confocal microscopy. Experimental results will provide fundamental of data about the pattern of hair cell differentiation and proliferation during sensory organ formation and will advance understanding of gene expression during inner ear development. The long term goal of this research is to identify the function of novel genes expressed in the inner ear, and to determine how genes expressed in the inner ear are regulated during development, regeneration, and aging. Results of these investigations will provide essential knowledge that can be used to develop effective treatments for hereditary and environmentally-induced disorders of hearing and balance.